98 S10 4X4 ISSUE

Seems unlikely that the "person" could even attain highway speed in 4 lo.

Did the transfer case actually change to 4 LO, or was it possibly just a problem with the dash/switch lite falsely showing 4 LO ??

As Dave said, it is not likely that anybody actually attained "highway" speed in actual 4 LO. Otherwise the engine and drivetrain are toast.

It's probably got a rev-limiter. Even my 92 Explorer has a Rev-limiter. Fastest you can go in LO is about 45. It seems unlikely anyone could drive it at highway speed just as has already been mentioned.

Having owned S-Blazer and S-10 P/U versions from 85 through our current

04 model, I can tell you that none of them will go faster than about 45 mph. At that speed the engine will be at red line rpm and would likely fail in less than 2-3 miles.

...

I do not know how fast or how far it went, and the engine did fail. My question is what would make it go into LO by itself? This has happened to me a couple of times, but I knew to switch it back to 2 HI before driving off.

More to the story....

I would bet on less than 3 miles as the engine would literally tear itself apart at those rpms.

I would also want to overhaul the T-Case as well. Very likely some damage from the abuse. Won't hurt to check the U-joints and change the lube in both axles if this was on clean pavement. The torque wrap would have heated things up a bit.

As to a cause: Bad switch unit or bad TCM. Either one could do it if they were hit with a voltage spike at start-up.

There's always more .. It is possible it was not in 4 LO when it happened. (I intend to question the clueless teenage driver more thoroughly) The mechanic who replaced the motor, told me it was in 4 LO when he got it from AAA and that was what blew the engine. I guess it could have been any number of things. Thanks for your help. I will have the T-Case & drive train checked out also.

If it was me "clueless teenager" would be "clueless teenager on bicycle"

I would check them out because of the stress that 4 wheel places on them if they get used on dry pavement. 4 hi for a long distance on dry pavement isn't good, 4 lo is VERY bad. At the least I would drop and change all the fluids in the transfer case, transmission, both axles. I would also suggest synthetics. Better in cold weather and more stable in hot weather.